This invention relates to novel solid heating fuels and, in particular, the invention is concerned with trioxane fuels of improved heat content.
Solid or gelled heating fuels have wide potential application as convenient, easily handled and comparatively safe heat sources. Such solid heating fuels in portable form can be employed in civilian uses such as camping, outdoor cooking of all sorts, fire-starting, emergency supplies, and the like. Solid heating fuels are also essential for military use, including the heating of field rations, etc.
A widely accepted form of solid heating fuel is trioxane formed from compaction of powdered trioxane with or without compaction aids such as magnesium stearate, a pure trioxane melt, or a trioxane melt mixed with an organic binder. Trioxane is a cyclic trimer of formaldehyde, molecular weight of 90 and has a melting point of 61.degree.-62.degree. C. Compacted or melted, molded or otherwise shaped and then cooled to a solid form, trioxane fuel such as in the shape of pellets is advantageous in view of the lack of toxicity and ease of ignition of this fuel. The low luminosity of trioxane fuel is especially useful for military applications.
One disadvantage of pure trioxane fuel is its low heat value, on the order of 7,200 Btu/lb. This low heat value is especially disadvantageous when trioxane is used as a heat source for heating field rations for military use. In a recent development, canned rations are being phased out in favor of meals ready-to-eat (MRE) in which a flexible package containing the meal is heated in a canteen of water to palatable temperature, i.e., 160.degree. F. (70.degree. C.). Because the heat is not applied directly to the food, MRE require a longer period of time to heat than canned rations. Accordingly, to meet the increased temperature requirement for MRE it is necessary to find a higher caloric content fuel than pure trioxane fuel. In view of the advantages of trioxane fuel such as previously discussed, in particular, the low luminosity, it would be beneficial to increase the caloric content of trioxane-based fuel if such enhanced heat content could be achieved without sacrificing the known advantages.
U.S. Pat. No. 3,355,269 is concerned with improving the caloric content of gelled fuel such as obtained from oxygenated hydrocarbons including ethyl acetayte; 1,4-dioxane; 1,3-dioxolane; diethyl carbonate; diethyl ether of ethylene glycol; dimethyl ether of diethylene glycol; trioxane, propyl acetate; butyl acetate; amyl acetate; hexyl acetate; methyl propionate; methyl butyrate; ethyl formate; diethyl ether of diethylene glycol; diethyl formal; dimethyl acetal; etc. This patent discloses mixing the oxygenated hydrocarbon fuel with a high molecular weight polymer prepared by reacting in the fuel, a semipolymer which is soluble in the liquid fuel and which comprises polyalkylenes or polyalkylidenes and polyethers, and a chain-extending agent which is a polyfunctional molecule containing two reactive groups such as aromatic polyisocyanate.
It is a primary object of the present invention to increase the heating value of trioxane fuels.
A further object of the invention is to increase the heating value of trioxane fuels without sacrificing the advantages of pure trioxane fuel such as lack of toxicity and ease of ignition. Still a further object of this invention is to enhance the heat content of trioxane fuel for military application without sacrificing the low luminosity of pure trioxane fuel.
These and other objects, aspects, and advantages of the invention will be readily apparent to those of ordinary skill in the art on consideration of the following description of the invention.